The distinctive form of the raised cottage - known in Milwaukee as
the "Polish flat." A 1911 Milwaukee housing study described the
typical process of expansion:

In the south side district, . . . the custom is to
erect first a four-roomed dwelling (or cottage). When this has been
paid for, it is raised on posts to allow a semi-basement dwelling to
be constructed underneath. This basement, or the upstairs flat, is
then let (rented) out by the owner, who, as soon as funds permit,
substitutes brick walls for the timber of the basement.

The particular advantage of the Polish flat was that once the
mortgage was paid, the flat could be converted back to a
single-family residence. Recently arrived immigrants created a
market for rental housing for which the raised cottage was ideally
suited. The raised cottage form appears in immigrant working-class
areas of Chicago and other midwestern cities as well. Apparently
because of its dominance in Polish immigrant neighborhoods, the
"raised cottage" earned the title of "Polish flat" in Milwaukee -
but only in Milwaukee.